Electrical inertial load controlling apparatus having gate drive for proctecting igbt

ABSTRACT

The present invention provides a gate drive for protecting a switching element (IGBT) used for an electrical inertial load controller. A high-voltage IGBT is used as the switching element and an hcp1316j is used as the gate drive of the IGBT, to restrict overvoltage and overcurrent generated in the event of inverter switching, preventing destruction of the IGBT in advance. Furthermore, an RC filter is formed in close proximity to the IGBT to minimize an erroneous switching operation due to harmonics generated caused by noise in case of inverter switching to improve the system reliability and block an increase in abnormal voltage applied across the switching element.

TECHNICAL FIELD

[0001] The present invention generally relates to a gate drive and, moreparticularly, to a gate drive of a large-capacity switching device usedfor an electrical inertial load controlling apparatus.

BACKGROUND ART

[0002] One of the essential elements for constructing an electroniccircuit system is the inverter serving as a switch. The principal pointsin constitution of the inverter are techniques for designing andmanufacturing a gate drive. This gate drive designing technique belongsto the electric power electronic field and employs a method ofincreasing a gate resistance or restricting overcurrent using a zenerdiode in the event of turn-off due to overcurrent or short-circuiting.

[0003] In general, the drive circuit of the switch used for theelectrical inertial load controller must operate in the environmentwhere very strong noise exists because a power converter should switcheselectric power. However, it is required that the noise does not affectthe operation of the controller. To solve the influence of the noise,accordingly, a cable for optical communication is used as a devicevarying with large power to electrically separate the controller andgate drive from each other.

[0004] The electrical inertial load controller conventionally employs ahigh-voltage IGBT (Isolation gate bipolar transistor) as its switchingelement. A conventional gate drive for protecting this IGBT includes aphoto-coupler operating by a signal applied from the outside, apre-amplifier for amplifying the signal outputted from thephoto-coupler, and a second drive driven by the signal amplified by thepre-amplifier.

[0005] The photo-coupler is constructed in a manner that alight-emitting device and a light-receiving device are contained in asingle package to transmit signals through the medium of rays of light.Specifically, the photo-coupler converts an electric signal into anoptical signal with the help of a light-emitting diode to transmit it,and restores a received optical signal into an electric signal using aphoto-transistor. The photo-coupler electrically isolates input andoutput from each other. The pre-amplifier, placed in front of a mainamplifier, amplifies a small output signal to some degree and reducesnoise.

[0006] However, the aforementioned gate drive of the high-voltage IGBTis currently being imported in high price, and its circuit configurationis complicated. In addition, the IGBT may be destroyed due toovervoltage or overcurrent generated in the event of inverter switching,to deteriorate the reliability of the entire system.

DISCLOSURE OF INVENTION

[0007] It is, therefore, an object of the present invention to provide agate drive that effectively blocks overvoltage or overcurrent generatedin the event of inverter switching of an electrical inertial loadcontroller to prevent destruction of IGBT serving as a switch.

[0008] Another object of the present invention is to provide a gatedrive of IGBT that minimizes generation of harmonics caused by noise inthe event of inverter switching of an electrical inertial loadcontroller.

[0009] A further object of the present invention is to provide a gatedrive of IGBT that reduces manufacturing costs.

[0010] To accomplish the objects of the present invention, there isprovided an electrical inertial load controller comprising an IGBTserving as a switch, an hcp1316j device serving as a gate drive fordriving the IGBT, and an RC filter, formed in close proximity to theIGBT, for preventing an erroneous switching operation due to harmonicsgenerated caused by noise in the event of switching of the IGBT andappropriately controlling the turn-on and turn-off time of the IGBT toreduce overvoltage applied across the IGBT in case of switchingoperation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Further objects and advantages of the invention can be more fullyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings, in which:

[0012]FIG. 1 is a block diagram of an hcp1316j applied to the presentinvention;

[0013]FIG. 2 is a circuit diagram of the hcp1316j applied to the presentinvention;

[0014]FIG. 3 shows control timing signals of the hcp1316j applied to thepresent invention; and

[0015]FIG. 4 shows voltage and current gate signals appearing across aswitch when the rising time and falling time of a switching signal werecontrolled using an RC filter.

BEST MODE FOR CARRYING OUT THE INVENTION

[0016] The present invention will now be described in connection withpreferred embodiments with reference to the accompanying drawings.

[0017]FIG. 1 is a block diagram of an hcp1316j applied to the presentinvention.

[0018] In the present invention, the hcp1316j shown in FIG. 1 is used asa gate drive. This hcp1316j prevents damages in devices and isolates aprocessor and a power converter from each other, through its overcurrentsoft turn-off function and imperfect operation of an output gate signaldue to low voltage.

[0019] In the present invention, in addition, to prevent erroneousoperations caused by a variety of noises generated in the gate signal ofthe IGBT and signal lines between devices, an RC filter is set in closeproximity to the IGBT. Specifically, the RC filter is being insertedbetween the base and emitter of the IGBT to remove noise transmittedthrough the gate signal line, thereby preventing an erroneous switchingoperation. Furthermore, the RC filter appropriately controls the turn-onand turn-off time of the IGBT to reduce overvoltage applied across theswitch in the event of switching thereof so that the dielectric strengthof the device can be designed in lower value, decreasing manufacturingcost.

[0020]FIG. 2 is a circuit diagram of the hcp1316j applied to the presentinvention. Referring to FIG. 2, pins 1 and 2 are parts to which controlsignals VIN+ and VIN− for switching are inputted. These signals aretransmitted to a secondary side through optical signals as long as afault signal is not outputted. A pin 13 designating a port Vcc2 iscompared with 12V to control an output signal in order not to output thecontrol signals to the IGBT in case of an under voltage of below 12Vthat is the minimum voltage capable of turning on a power switch safely.

[0021] A pin 14 indicating a port DESAT is connected to the powerswitch, that is, the collector of the IGBT, and a pin 16 designating aport VE is connected to its emitter so that a voltage drop in the switchis increased when current flows through the IGBT, raising the voltage ofthe port DESAT 14. Here, when the voltage drop caused by overcurrentincreases by 7V or more, the switch is turned off to protect the device.However, if hard turn-off is carried out for the switch, abnormalovervoltage is generated to destroy the IGBT. Thus, it is preferablethat the IGBT is turned off with a predetermined delay time, as shown inFIG. 3.

[0022]FIG. 4 shows voltage and current gate signals appearing across theswitch when the rising time and falling time of a switching signal werecontrolled using the RC filter. As shown in FIG. 4, the rising time andfalling time of the gating signal are properly adjusted to prevent anincrease in abnormal voltage.

[0023] As described above, the present invention uses the high-voltageIGBT as a switch of an electrical inertial load controller to restrict atrouble that may be generated in the gate drive, that is, overvoltageand overcurrent created in case of inverter switching, to preventdestruction of the IGBT in advance. Furthermore, the invention minimizeserroneous switching operation due to generation of harmonics caused bynoise in the event of inverter switching to improve the systemreliability and to block an increase in abnormal voltage across theswitch, generated in case of switching operation.

[0024] Although specific embodiments including the preferred embodimenthave been illustrated and described, it will be obvious to those skilledin the art that various modifications may be made without departing fromthe spirit and scope of the present invention, which is intended to belimited solely by the appended claims.

What is claimed is:
 1. An electrical inertial load controller having a gate drive for protecting an IGBT, comprising: an IGBT serving as a switch; an hcp1316j device serving as the gate drive for driving the IGBT; and an RC filter, formed in close proximity to the IGBT, for preventing an erroneous switching operation due to harmonics generated caused by noise in the event of switching of the IGBT and appropriately controlling the turn-on and turn-off time of the IGBT to reduce overvoltage applied across the IGBT in case of switching operation.
 2. The electrical inertial load controller as claimed in claim 1, wherein the RC filter is being inserted between the base and collector of the IGBT. 